1. Field of the Invention
Data communication systems involving both two-way and one-way only communication links.
2. Description of the Prior Art
A number of data transmission systems exist which require certain restrictions on transmissions between different classifications of equipment.
For example, in a nuclear power generating complex, hundreds of remote stations may be located throughout the complex for gathering, by means of sensors, data relative to radiation levels, pressures, temperatures, and wind and fluid flows, to name a few. Each of the remote stations includes a computer means for handling the data and for transmitting such data back to a central control room for display, interpretation and any necessary action.
There are two classes of remote stations, a first being a safety type which can automatically operate to provide various safety functions if required, without human intervention. These safety remote stations are in two-way communication with a primary, or safety console which may be located in the central control room and which is operable to request and receive data from these safety remote stations. The safety class equipment requires special qualification tests and fabrication controls to quarantee its operability under a wide range of accident conditions.
A second type of classification for a remote station is a non-safety or control station which is in two-way data communication with a non-safety, or secondary console within the control room. This secondary console is also operable to receive the data transmitted by the safety remote stations with the restriction that it may not transmit requests for data to these safety remote stations nor may it be in communication with the primary console relative to such requests for data.
Accordingly, the primary console requests data without the knowledge of the secondary console which is to receive such data. The present invention provides a means for accomplishing such operation with minimal requirements for hardware and data communication cabling.